fix a bug in update_continuum
fix a bug in update_continuum

It will casue the valgrind to report "Conditional jump or move depends on uninitialised value(s)"

mckelvin/libmemcached,tony2001/libmemcached,tony2001/libmemcached,tony2001/libmemcached,mckelvin/libmemcached,mckelvin/libmemcached